Does using $this-> in a Singleton class violate the pattern or is it considered bad practice?

Using `$this->` in a Singleton class is not recommended as it can potentially violate the pattern by allowing multiple instances to be created. It is considered bad practice because the whole point of a Singleton is to have only one instance of the class. To ensure the Singleton pattern is correctly implemented, you should access the instance through a static method instead of using `$this->`.

class Singleton {
    private static $instance;

    private function __construct() {
        // private constructor to prevent instantiation
    }

    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }
}